Adding radioimmunotherapy to chemo may help patients with lymphoma

Patients treated for follicular lymphoma, a slow-growing type of non-Hodgkin's lymphoma, may benefit from chemotherapy followed by radioimmunotherapy, according to a University of Pittsburgh Medical Center (UPMC) study presented at the annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago and published as Abstract 8005 in the ASCO proceedings.

Over 90 percent of study patients responded completely to the treatment and since only a short-course of chemotherapy was used, side effects were limited and well-tolerated. Radioimmunotherapy was delivered through the use of a radiolabeled monoclonal antibody specifically designed to kill lymphoma cells with the help of a radioactive atom.

"We found that adding a radioactive monoclonal antibody to standard chemotherapy helped lymphoma patients achieve a higher complete response rate. We hope that this will translate into long-lasting remissions," said Samuel Jacobs, M.D., lead investigator and associate director for clinical investigations at the University of Pittsburgh Cancer Institute and UPMC Cancer Centers.

In the study, a radiolabeled monoclonal antibody called ibritumomab tiuxetan (IT) was added to CHOP-R, a standard multi-drug regimen for follicular lymphoma that consists of cyclophosphamibe, doxorubicin, vincristine, prednisone and rituximab. Investigators reported on 50 patients treated with CHOP-R, examined their responses and then treated them with IT. Sixty-eight percent of the patients had a complete response to treatment with CHOP-R. This percentage increased to 96 percent after treatment with IT.

The complete response rate was determined by both conventional CT and the use of PET, or positron emission tomography, a scan that measures abnormal molecular cell activity. PET was used to determine which patients had an early complete disease response after treatment with chemotherapy alone and after treatment with IT. The researchers found that five out of 16 patients who had a positive PET scan after the initial chemotherapy phase of treatment relapsed. Of the 34 patients whose early PET scans were negative, none have relapsed to-date.

"We were surprised to find that PET was a useful tool in determining those patients who were at highest risk for their diseases to relapse. Our next step is to compare the tumor characteristics of the patients who relapsed to those who had an early complete response," said Dr. Jacobs.